The present invention relates to graphic codes and in particular graphic codes that are defined by a code window.
Codes that are graphically represented and machine-readable are well-known. Such codes are commonly used on consumer and commercial products and when read may provide information relating to the cost, line item, or origin of the product, for example. These types of codes may be used for automating check-outs at supermarkets, for stock control purposes or for verifying the correct product is in the correct packaging. More complex machine-readable codes of this type can be used as a security feature on certain consumer products such as pharmaceuticals, alcohol, tobacco and the like or for documents of high value such as currency, bonds, tax stamps, travel documents and identification cards to prevent counterfeiting, pass-off and diversion. There are a number of different types of code formats commonly in use; these include alphanumerics, linear barcodes and two-dimensional barcodes. However, these types of codes are relatively simple to copy. It may also be possible to guess the next code within a sequence since the algorithms used to generate such codes are in the public domain. Also, information is encoded within the code, and even if the data is encrypted, the information can be derived from the code without reference to any database. The data may be used or manipulated for unauthorised purposes; which greatly reduces the effectiveness of such codes as security or track and trace devices.
One sophisticated type of machine-readable code is described in our UK Patent no GB 2383878 (the entire contents of which are incorporated herein by reference) and commercially available under the trademark FractureCode®. Advantages of this type of code over other commercial machine-readable codes include the ability to generate a very high number of random unique codes. Another major advantage is that the code itself carries no data and no data is required to generate the code at the time of the code is printed. This renders the code meaningless until the moment it is used.
Articles, such as documents of value and consumer products, such as those already mentioned, or their packaging, are marked with such codes. In order to obtain information about an article bearing a code, the code must be read by a machine, which first performs a scanning operation to acquire digitally an image of the code. The image is then processed electronically to derive, via application of an algorithm, a unique alphanumeric descriptor that may be used to look up data corresponding to the article in a database.
The code is typically located on the surface of an article and comprises a unique graphical pattern, composed of lines, dots or ellipses or other markings or combinations of these, with an area of the pattern delimited by a rectangular box or some other graphical boundary to form a physical code window. In order to print this unique graphical indicium special printing apparatus must be used.
It is particularly difficult to copy this code for a number a reasons.
Firstly, it is difficult to reproduce the code with the degree of accuracy required, i.e. such that a reading machine would fail to distinguish between the line position of an original code and that of a copy and would generate the same alphanumeric descriptor as would have been generated when scanning the original code. This feature is partly a function of the level of detail of the code.
Secondly many of the codes are no more than 1 mm by 1 mm in area and may be printed in ultraviolet inks, infrared inks or other convert security inks.
A major security advantage of these codes is that without the decoding algorithm the alphanumeric descriptor cannot be deduced. Further, even if the algorithm were to be known, the data corresponding to the alphanumeric descriptor cannot be obtained without access to a secure database.
Although these codes are difficult to copy and guess, since only the area delimited by the rectangular box, or some other graphical boundary, is of any interest, the only portion that needs to be reproduced by any unauthorised user is the code window and the area within it. This means that the whole of the graphical pattern on the substrate need not be copied and any line pattern not within the code window is effectively redundant. Furthermore, someone wishing to read the code without authorisation knows which part of the graphical pattern to look at since it is surrounded by a rectangular box or some other graphical boundary.
A further consideration is that whilst increasing the size of the window would make it more difficult to forge or replicate the code since more code would have to be copied, due to aesthetics the size of the window must be kept small so that it does not interfere with the product graphics on the packaging or data on a document.
WO 2005/080088 discloses an object (e.g. a bank note or a cheque) comprised of a primary identifier. The primary identifier is in the form of a plurality of identification elements embedded in the object, which are visually detectable when illuminated by infrared or ultraviolet electromagnetic radiation but are visually indistinguishable from the rest of the object when illuminated with visible light. The identification elements are randomly distributed so that the positions of the identification elements are practically unique to the object, and the object has a reference point in the form of a printed symbol which defines a sub-area of the object in which at least some of the identification elements are provided. A method and a detector for verifying that such an object is genuine are also described. The object is verified by comparing measured information relating to the positions of the identification elements in the sub-area relative to the reference point, with recorded information of the genuine object.
There are several disadvantages associated with such a system. Firstly, the pattern of the random distribution of identification elements is determined completely by chance. Therefore its uniqueness cannot be guaranteed and unwanted replication cannot be mathematically ruled out. Secondly, the reference point defines an area which is used to identify the object. Although the reference point may not indicate the size and shape of the identifying area, it inevitably suggests the location of this area. Thirdly, if a plurality of identifying areas are desired, for example, for reasons of added security, this can only be achieved by having a plurality of reference points to define the respective identifying areas. This may interfere with the aesthetics of the object, or more importantly, reveal the significance of the reference points to a potential counterfeiter.
It is therefore desirable to provide a code which is even more covert, making it more difficult to copy, tamper with or read without authorisation.